Add soport for timestamp type fields.

Problem/Motivation

Hello.

I am using your module with a timestamp type field. I had to make some changes to the code of your module so that the date type filters work with a timestamp type field. It would be correct for the module to be able to use it and with the timestamp type fields.
I simply add the strtotime function in the filters of your module. And I'm not sure with the other types of date fields if it would work. At the moment things are going well for me in my environment.

Thank you.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes